U.S. patent number 4,843,427 [Application Number 07/140,822] was granted by the patent office on 1989-06-27 for selective charge removal system for copier.
This patent grant is currently assigned to Sharp Kabushiki Kaisha. Invention is credited to Yoshiaki Ibuchi.
United States Patent |
4,843,427 |
Ibuchi |
June 27, 1989 |
Selective charge removal system for copier
Abstract
A selective charge removal system for a copier uses a
transparent electrochromic display with many segments or dots
thereon and a back-lighting unit such that only a specified area
which is precisely defined on the photosensitive body of the copier
is exposed to the light from the back-lighting unit. These segments
or dots are driven to an intermediate color state during a wait
period before a copying operation of the copier is started such
that the color conditions of the electrochromic display can be
changed quickly.
Inventors: |
Ibuchi; Yoshiaki (Nara,
JP) |
Assignee: |
Sharp Kabushiki Kaisha (Osaka,
JP)
|
Family
ID: |
26333766 |
Appl.
No.: |
07/140,822 |
Filed: |
January 5, 1988 |
Foreign Application Priority Data
|
|
|
|
|
Jan 5, 1987 [JP] |
|
|
62-718 |
Jan 5, 1987 [JP] |
|
|
62-719 |
|
Current U.S.
Class: |
399/186; 359/271;
359/275; 399/81 |
Current CPC
Class: |
G03G
15/047 (20130101) |
Current International
Class: |
G03G
15/045 (20060101); G03G 15/047 (20060101); G03G
015/00 () |
Field of
Search: |
;355/3R,7,14E,40,71
;350/356,357 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Grimley; A. T.
Assistant Examiner: Pendegrass; J.
Attorney, Agent or Firm: Flehr, Hohbach, Test, Albritton
& Herbert
Claims
What is claimed is:
1. In a selective charge removal system for a copier, said copier
comprising
a photosensitive body,
charging means for charging said photosensitive body,
developing means for developing an image on said photosensitive
body,
light-emitting means disposed between said charging means and said
developing means for selectively removing charge either from an
electrostatic latent image formed on said photosensitive body or
from a specified area on said photosensitive body for forming an
electrostatic latent image thereon, and
control means for controlling the operation of said light-emitting
means,
the improvement wherein said light-emitting means comprise
a transparent electrochromic display having a plurality of segments
or dots arranged thereon, and
a back-lighting unit,
said control means including driving means for driving each of said
segments or dots into an intermediate color condition during a wait
period prior to a copying operation of said copier, said
intermediate color condition being a state between the colored and
colorless states of said segments or dots, whereby the display
conditions of said electrochromic display can be changed more
quickly.
2. The system of claim 1 wherein said electrochromic display is
disposed between said back-lighting unit and said photosensitive
body.
3. The system of claim 1 wherein said electrochromic display
comprises a first transparent plate and a second transparent plate
disposed in a mutually parallel relationship with respect to each
other, said segments or said dots being disposed on said first
transparent plate, a transparent electrode being disposed on said
second transparent plate said first transparent plate being covered
with an electrochromic material, and said first and second
transparent plates sandwiching an electrolyte therebetween.
Description
BACKGROUND OF THE INVENTION
This invention relates to a selective charge removal system with
which an image produced by a copier can be erased selectively by
preliminarily removing charge from specified areas on its
photosensitive body.
When the original document to be copied by a copier is too thick or
somewhat smaller than a standard size and the copier is operated
with its document cover in the open position, undesirable black
marks may appear along the edges of the produced copy. On the other
hand, some modern copiers are provided with capabilities for
editing operations such as trimming, masking, centering and
two-color copying by combining these modes of operations. To
perform such operations, the user specifies an area on the original
by means of numeric keys or a stylus pen and a light-emitting
device provided to the copier selectively erases the electrostatic
latent image formed on the photosensitive body. Such a
light-emitting device typically comprises a large number of
light-emitting diodes mutually screened apart by screening plates
and disposed in a single column along a straight line perpendicular
to the direction of transportation of copy sheets. The unsightly
black marks along the edges and the like can thus be erased by such
a device but a device with many light-emitting diodes arranged in a
line is difficult to assemble and inconveniently costly. Moreover,
the resolution of such a light-emitting device is determined by the
pitch of the constituent diodes which is usually as big as about
2.5-2.7 mm and this means that charge cannot be removed very
accurately.
In the case of a composite copying mode of operation in two colors
by using the masking method, for example, the problem of resolution
may arise as follows. With reference to FIG. 1 which shows the
positional relationship between a specified area on an original
document to be copied and a light-emitting device as well as the
image which is copied, a rectangular area is specified by inputting
the positions of its diagonal corner points such as P.sub.1 and
P.sub.2 such that the areas inside and outside this rectangle are
copied in different colors M and N, respectively. Along the
boundary lines which are perpendicular to the direction of the
light-emitting device (indicated by numeral 7), however, the two
colors may overlap or there may appear an area with no color at all
because of the inadequate resolution as shown by letter L.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to eliminate the
disadvantages of the prior art selective charge removal system for
a copier and to provide an inexpensive light-emitting device and a
new selective charge removal system with improved resolution.
The above and other objects of the present invention are achieved
by providing a selective charge removal system for a copier with a
light-emitting device which comprises a transparent electrochromic
display with many segments or dots and a back-lighting unit. Charge
is removed from the surface of the photosensitive body of the
copier because this transparent electrochromic display serves to
selectively allow the light from the back-lighting unit to pass
therethrough. Since segments and dots can be arranged at a narrower
pitch in an electrochromic display than conventional light-emitting
diodes, charge can be removed from a specified area with improved
resolution.
In another aspect of the present invention, the charge removal
system further comprises means for controlling the operation of the
display such that each segment or dot of the display is driven to a
state of having an intermediate color during a wait period prior to
the start of a copying operation. Although electrochromic displays
using a conventional electrochromic material generally have a
slower response time than display devices of other types, the
aforementioned method of the present invention serves to speed up
the operation of coloring and erasing because the segments and dots
are initially in an intermediate color state.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and form a
part of the specification, illustrate embodiments of the present
invention and, together with the description, serve to explain the
principles of the invention. In the drawings:
FIG. 1 is a drawing for explaining problems encountered by a prior
art copier,
FIG. 2 is a schematic sectional view of a copier incorporating a
selective charge removal system embodying the present
invention,
FIG. 3 is a perspective view of a light-emitting device in the
copier of FIG. 2,
FIGS. 4A and 4B are respectively a front view and a side sectional
view of the light-emitting device of FIG. 3,
FIG. 5 is a perspective view of an electrochromic display in the
light-emitting device of FIG. 3,
FIG. 6 is a sectional view of a part of the electrochromic display
of FIG. 5,
FIG. 7 is a circuit diagram of the final stage of a driver circuit
for operating the electrochromic display of FIGS. 5 and 6,
FIG. 8 is a graph showing the relationship between transmissivity
and wavelength of the electrochromic display of FIGS. 5 and 6 in
its on and off states,
FIG. 9 is a graph showing the time-rate of change in transmissivity
of the electrochromic display of FIGS. 5 and 6,
FIG. 10 is a block diagram of the control unit of the copier of
FIG. 2, and
FIG. 11 is a flow chart of the operation of the central processing
unit of FIG. 10.
DETAILED DESCRIPTION OF THE INVENTION
With reference to FIG. 2 which shows the structure of a copier
incorporating a selective charge removal system embodying the
present invention, a photosensitive drum 20 is disposed nearly at
the center of the copier housing, surrounded by various units for
performing the copying process such as a primary charger 21, a
light-emitting device 7, a first developing unit 22a, a second
developing unit 22b, a transfer and paper removal charger 23 and a
cleaner unit 24. The light-emitting device 7 is for selectively
removing charge from the surface of the photosensitive drum 20
charged by the primary charger 21 and includes, as will be
explained more in detail later, a back-lighting unit and an
electrochromic display. A copy paper sheet selectively supplied
from one of cassettes 36a, 36b and 36c is transported in the
direction of the photosensitive drum 20 through synchronization
rollers 35. After a toner image is transferred onto the sheet, the
image is fixed by fixing rollers 25 and the sheet is transported by
the operations of claws 26 and 27 either directly into a discharge
tray 31 or temporarily into another tray 29 from which it is
transported backwards by reverse rollers 28 into the discharge tray
31 through rollers 30. A choice between these two modes of paper
transportation is made, depending on whether copying is effected on
both sides of the copy paper or a composite copy is desired on one
side. If copying is to be effected for the second time on a sheet
which is already in the discharge tray 31, rollers 31a and 31b are
used to selectively transport only the top sheet in the discharge
tray 31 in the direction of the synchronization rollers 35 through
rollers 32, 33 and 34.
The light-emitting device 7 for removing charge selectively from a
specified area on the photosensitive drum 20, as shown in FIGS. 3,
4A and 4B, comprises an electrochromic display 70 which is fastened
to a metallic base frame 80 of a circuit board by means of an angle
plate 79. An indentation is formed in the base frame 80 and
contains the electrochromic display 70 connected electrically
through connectors 83a, 83b, 83c and 83d. The space formed between
the display 70 and the indentation in the base frame 80 contains a
back-lighting unit comprised of four lamps 82a, 82b, 82c and 82d
and a reflective case 81. With a light-emitting device thus formed,
light from the back-lighting unit can be selectively introduced to
the surface of the photosensitive drum 20 by switching on and off
each segment of the electrochromic display 70.
The electrochromic display 70 is formed between two glass plates 71
and 72 as shown in FIGS. 5 and 6. One of the glass plates (71) is
provided on its surface with a plurality of segments 75 made of a
transparent electroconductive film, and this surface is covered
with an electrochromic material 74. The other glass plate 72 has an
electrode 76 of a transparent electroconductive film formed over
its entire surface and an electrolyte 73 is contained between these
two glass plates 71 and 72. A sealing material 78 is used along the
periphery of the area over which these plates 71 and 72 are placed
opposite each other to seal the electrolyte 73 inside. Conductive
pieces 77 for making contacts with the transparent electrode 76 are
provided at specified positions inside this sealing material 78. A
blue display can be made if tungston oxide is used as the
electrochromic material 74 and a negative charge is transmitted to
the segment from the opposite electrode and the color can be made
to disappear if a current is passed in the opposite direction. If
iridium hydroxide is used as the electrochromic material, a display
in gray can be made and erased similarly. Such a choice is made
generally according to the sensitivity characteristics of the
photosensitive drum. With reference next to FIG. 7 which shows the
final stage of a circuit for driving the electrochromic display
explained above, the transistor Q.sub.2 is switched on if a
negative voltage -V is applied to the input terminal IN and the
segment 75 becomes colored. The transistor Q.sub.1 is switched on
if a positive voltage +V is applied and the segment 75 becomes
colorless. FIG. 8 shows that the electrochromic display 70 has a
particularly high contrast in transmissivity between the on
(colored) and off (colorless) states in the visible range wherein
the photosensitive drum is sensitive. In other words, the
electrochromic display 70 is capable of selectively removing charge
with sufficient accuracy.
With reference next to FIG. 9 which shows the time-rate of change
in transmissivity of the electrochromic display 70, the curve A-P-B
represents the change in transmissivity if a coloring current is
passed through it when it is initially (at t.sub.1) in the off
condition with its transmissivity da and the curve C-P-D represents
the change if an erase current is passed through it when it is
initially (at t.sub.1) in the colored condition with its
transmissivity dc. The point P represents a condition in which the
electrochromic display 70 has an intermediate color of transparency
dp. The time required to color the display 70 from this
intermediate color condition is t.sub.3 -t.sub.2 and the time
required to erase the color from this intermediate color condition
is also t.sub.3 -t.sub.2. In other words, a desired (colored or
colorless) display can be obtained relatively quickly (compared to
t.sub.3 -t.sub.1) if the display 70 is operated from this
intermediate color condition.
FIG. 10 is a block diagram of the control unit of the copier shown
in FIG. 2 and described above as incorporating a light-emitting
device of the present invention. The overall control is carried out
by a central processing unit CPU 1 according to a program
preliminarily stored in a read-only memory ROM 2. A random-access
memory RAM 3 is used as various working areas in the execution of
this program. Numeral 4 indicates a display memory for storing the
contents of display by the electrochromic display 70. Such a stored
content of display is adapted to be retrieved by a display
controller 5 which outputs a corresponding display control signal
to a driver 6. The driver 6 contains a driver circuit shown in FIG.
7 at its output end and serves to selectively color or erase the
segments of the electrochromic display 70. Numeral 9 indicates a
relay for performing the on/off control of the back lamps 82. The
CPU 1 activates the relay 9 through an I/O port 8 according to an
appropriate timing schedule. Numeral 11 indicates a control panel
having as an input means through which the user can specify an area
on an image in an editing mode of operation such as trimming and
masking. The inputted information is received by the CPU 1 which,
in turn, records it in the display memory 4. Also connected to the
I/O port 8 are a copy lamp, a heater lamp for the fixing rollers
25, motors for driving the rollers, all kinds of sensors for
detecting, for example, whether a copy paper sheet has been
supplied, etc. With a control unit thus structured, the CPU 1
monitors the elapsed time from the starting of an operation and
after a specified time interval, an on/off pattern for the
electrochromic display 70 is written in the display memory 4. At
the same time, a display control signal is transmitted to the
display controller 5 for a desired display. The relay 9 is also
activated according to a specified timing schedule to control the
back lamps 82.
The operation of the CPU 1 outlined above is explained next by way
of the flow chart shown in FIG. 11. According to a mode of
operation embodying the present invention, the CPU 1 starts by
transmitting to the display controller 5 a command to drive the
electrochromic display 70 into the intermediate color defined above
in connection with FIG. 9 (n1). When this command is received, the
display controller 5 causes an erase current to flow for a time
duration given by t.sub.3 -t.sub.2 of FIG. 9 to those segments
which are already in the colored state and a coloring current
likewise to those segments which are in the off state. As a result,
all segments are driven to the intermediate color condition.
Thereafter, the CPU 1 interprets the operated keys (n2). If the
user operates a key or keys to set the copying conditions (n5 after
NO in n3), such conditions are set. If the user does not operate
any key (NO in n3 and n4), the size of the original document to be
copied is detected (n6) and display data representing the area from
which charge should be removed according to the detected document
size are recorded in memory 4 (n8). A ready lamp for indicating
that the copier is ready for a copying operation is thereafter
switched off (n9) and a command signal is transmitted to the
display controller 5 to drive the electrochromic display 70
according to the contents of the display memory 4 (n10).
If the driver 6 completes the operation of the electrochromic
display 70 (YES in n11), the CPU 1 switches off the ready lamp
(n12). If it is detected that the document being copied has moved
or otherwise that the document area has changed (YES in n7),
display data are reentered (n8) as explained above.
If the print key (not shown) of the copier is operated after the on
and off states of the electrochromic display 70 are determined (YES
in n3), the ready lamp is turned off (n14) and the regular copying
operation is carried out (n15). During such a copying operation,
the back lamps are turned on (n152) whenever the time to do so is
detected (n151) and they are kept turned off at other times (n153).
After the copying operation is completed, the ready lamp is turned
on again (n16) and all segments of the electrochromic display 70
are driven to the intermediate color (n1). The advantage of setting
all segments in the intermediate color before each copying
operation is started is that the display condition can be changed
quickly as soon as the document area is determined.
In summary, the present invention discloses a light-emitting device
comprised of a transparent electrochromic display with many
segments or dots and a back-lighting unit for selectively removing
charge from the surface of the photosensitive body. As a result,
charge can be removed with an extremely small pitch and hence with
an extremely high resolution. Thus, composite copying can be
effected without overlapping or missing areas at the boundaries.
Since it is no longer necessary to assemble a large number of
light-emitting elements, the cost can be reduced. With the driving
method of the present invention, furthermore, a display can be made
quickly even with a display device with a relatively slow response
time.
The foregoing description of preferred embodiments of the invention
has been presented for purposes of illustration and description. It
is not intended to be exhaustive or to limit the invention to the
precise form disclosed, and many modifications and variations are
possible in light of the above teaching. For example, the segments
75 shown in FIG. 6 may be replaced by dot electrodes as mentioned
above. Any modifications and variations that may be apparent to a
person skilled in the art are intended to be included within the
scope of this invention.
* * * * *